The present invention relates to the field of hydrocarbon upgrading processes. In another aspect, the invention relates to the conversion of heavy hydrocarbon streams to aromatics and ethylene, propylene and butylene.
Developments in zeolite catalysts useful in hydrocarbon conversion processes have led to the use of zeolite catalysts for the conversion of heavy hydrocarbon streams containing heavy olefins to aromatics without the addition of hydrogen. The conversion of C.sub.2 -C.sub.4 alkanes and alkenes to produce aromatics using zeolite catalysts was found to be an effective process by both Cattanach (U.S. Pat. Nos. 3,760,024 and 3,756,942) and Yan et al. (U.S. Pat. No. 3,845,150). Nemet-Marrodin et al. have added to the understanding of the conversion of heavy hydrocarbon streams containing heavy olefins to aromatics using zeolite catalysts by suggesting the use of a purified recycle stream in U.S. Pat. No. 5,186,908. Other patents representative of aromatization of heavy hydrocarbon streams containing heavy olefins using zeolite catalysts include Young, U.S. Pat. No. 4,356,338, which discloses reducing coke formation on zeolite catalysts by treating the catalyst with phosphorus and steam, and Tabak et al., U.S. Pat. No. 4,751,338, which discloses continuous catalyst regeneration and the recycle of C.sub.5 + aliphatics in a fluidized bed.
These processes are effective in preferentially converting heavy hydrocarbons to aromatics at the expense of light olefin yield. Also, there is limited flexibility in these processes to shift the conversion of heavy hydrocarbons from aromatics to light olefins. Therefore, development of a process for converting heavy hydrocarbons to aromatics and light olefins wherein the yield of light olefins is enhanced would be a significant contribution to the art and to the economy by allowing the flexibility to preferentially convert heavy hydrocarbons to either aromatics or light olefins depending on market conditions.